Conventional electrical metal clad (MC) fittings or connectors may require several connector sizes and/or multiple parts to engage one armored cable diameter or a range of armored cable diameters. This requires distributors to inventory several connector parts or connectors for each diameter range and/or each trade size. To reduce the overall number of connectors needed and to maximize existing resources, connectors are commonly rated for use with a variety of cables and conduits. For instance, MC connectors are listed for use with MC cable, flexible metal conduit (FMC), and in some cases Nonmetallic (NM) Cable.
Dimensional criteria for selecting an appropriate connector may include trade size (knockout (KO)), cable diameter (i.e. jacket and/or armor diameter) range, and end stop (throat) diameter. For example, when a throat diameter is too large in a connector, the throat diameter will permit cables with smaller armor diameters to pass through the end stop. In contrast, when the end-stop is too small, the number and size of conductors that can pass through the end-stop are limited. Thus, the number of connectors needed to cover an available cable size range is increased. Also, connector assemblies that have “numerous” parts or pieces have an increased tendency for creating worker frustrations or even work stoppage should any of these pieces become missing or lost altogether.
Additionally, features that minimize or eliminate installation errors are not currently available among conventional MC connectors. For instance, with respect to interlocked armor cable, one end of the cable has a tendency to expand to a larger diameter than the other end of the same cable during termination. Thus, depending upon which end is being terminated, interlocked armor cable may require two (2) different connector sizes for the opposite ends of the cable. Further, with regard to continuously welded and corrugated armor (CWA), connectors that use “thread-on” features were developed to provide intimate contact between the connector and the armor for sealing and electrical bonding. Other non-threaded fittings that are available for CWA usually have additional components or parts for creating a seal between the cable and the connector for hazardous location ratings, again adding costs and pieces that are not necessary for dry-location-only ratings. Thus, the introduction and rapid market growth of MC cables has exacerbated issues associated with the compatibility between connectors and cables.